Fasting Diets

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

Fasting diets introduction

Fasting to lose weight is nothing new, but a new crop of trendy diets has
brought the practice back into the spotlight.

Diets like the 5:2 Diet, Lemonade Diet, and others claim to help people lose
weight fast and detoxify the body, but the research to support those claims is
spotty at best.

What are intermittent fasting diets?

The 5:2 diet was recently the topic of a popular BBC documentary and book,
and it's based on the principle of intermittent fasting (IF) or alternate-day
fasting (ADF). Intermittent fasting means you eat normally at certain times and
then fast or dramatically reduce your calorie intake at other times.

The 5:2 diet calls for eating normally on five days of the week and fasting
(eating no more than 500 calories for women and 600 for men) on the remaining
two days. Proponents of the 5:2 diet and similar fasting diets claim that they
can increase lifespan, improve how the brain works, and protect against disease;
but most of those claims are based on research conducted in animals like rats
and mice.

There are some small studies in humans that suggest that intermittent fasting
diet may help promote
weight loss and reduce risk factors for heart disease,
diabetes, and other
weight-related health problems. For example, a small 2012 study in Nutrition and
Metabolism showed 30 obese women who followed a liquid intermittent fastingF diet lost 8.8 pounds
and 2.3 inches from their waistlines after eight weeks. (Excess body fat around
the waist has been associated with a higher risk of heart disease.)

Another 2012 study in Nature suggests that the life-extending benefits
rodents gained on fasting diets may not translate to larger and more human-like
animals, like monkeys.